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P Amlot

Publications and source records attributed to P Amlot.

At least 19 recordsLinked to original sources
PubMed2006

What delay should there be between primary infectious mononucleosis and renal transplantation?

A 17-yr-old girl in end-stage renal failure was due to undergo living-related pre-emptive renal transplantation when she developed acute infectious mononucleosis (AIM) from Epstein-Barr virus (EBV). In view of the risk of post-transplant lymphoproliferative disorder (PTLD) we were unsure as to the optimal delay between AIM and renal transplantation. This report describes the process used to determine maturation of the immune response to EBV using a combination of serology, immunophenotyping and molecular viral load estimation. These tests showed that EBV had not been cleared and dialysis was instituted rather than proceed directly to transplantation. After EBV viral load became undetectable in the blood, living-related donor was successfully performed 13 months after AIM. With 42-month post-transplant follow up there has been no evidence of PTLD.

Adolescent↗
PubMed2004

Modifying an immunogenic epitope on a therapeutic protein: a step towards an improved system for antibody-directed enzyme prodrug therapy (ADEPT).

Carboxypeptidase G2 (CP) is a bacterial enzyme, which is targeted to tumours by an antitumour antibody for local prodrug activation in antibody-directed enzyme prodrug therapy (ADEPT). Repeated cycles of ADEPT are desirable but are hampered by human antibody response to CP (HACA). To address this, we aimed to identify and modify clinically important immunogenic sites on MFECP, a recombinant fusion protein of CP with MFE-23, a single chain Fv (scFv) antibody. A discontinuous conformational epitope at the C-terminus of the CP previously identified by the CM79 scFv antibody (CM79-identified epitope) was chosen for study. Modification of MFECP was achieved by mutations of the CM79-identified epitope or by addition of a hexahistidine tag (His-tag) to the C-terminus of MFECP, which forms part of the epitope. Murine immunisation experiments with modified MFECP showed no significant antibody response to the CM79-identified epitope compared to A5CP, an unmodified version of CP chemically conjugated to an F(ab)(2) antibody. Success of modification was also demonstrated in humans because patients treated with His-tagged MFECP had a significantly reduced antibody response to the CM79-identified epitope, compared to patients given A5CP. Moreover, the polyclonal antibody response to CP was delayed in both mice and patients given modified MFECP. This increases the prospect of repeated treatment with ADEPT for effective cancer treatment.

Animals↗
PubMed2004

Subacute immune response to primary EBV infection leading to post-transplant lymphoproliferative disease in a renal transplant patient.

A 23-year-old man sero-negative for Epstein-Barr virus (EBV) developed recurrent sore throats 3 and 6 months after a renal transplant from an EBV sero-positive donor. Tonsillar biopsy at 9 months post-transplant showed post-transplant lymphoproliferative disease (PTLD) caused by EBV. Following reduction of immunosuppressive treatment, he developed further signs and symptoms, and serological evidence of infectious mononucleosis followed by resolution of lymphadenopathy. This case emphasizes the difficulty in interpreting EBV serology in immunosuppressed patients and the importance of pre-transplant EBV serology.

Adult↗
PubMed2001

Immunoglobulin heavy-chain gene rearrangement in adult acute lymphoblastic leukemia reveals preferential usage of J(H)-proximal variable gene segments.

The aim of this study was to characterize individual-segment and overall patterns of V(H) gene usage in adult B-lineage acute lymphoblastic leukemia (ALL). Theoretical values of V(H) segment usage were calculated with the assumption that all V(H) segments capable of undergoing rearrangement have an equal probability of selection for recombination. Leukemic clones from 127 patients with adult B-lineage acute leukemias were studied by fingerprinting by means of primers for the framework 1 and joining segments. Clones from early preimmune B cells (245 alleles identified) show a predominance of V(H)6 family rearrangements and, consequently, do not conform to this hypothesis. However, profiles of V(H) gene family usage in mature B cells, as investigated in peripheral blood (6 samples), B-cell lymphomas (36 clones) and chronic lymphocytic leukemia (56 clones), are in agreement with this theoretical profile. Sequence analyses of 64 V(H) clones in adult ALL revealed that the rate of V(H) usage is proportional to the proximity of the V(H) gene to the J(H) locus and that the relationship can be mathematically defined. Except for V(H)6, no other V(H) gene is excessively used in adult ALL. V(H) pseudogenes are rarely used (n = 2), which implies the existence of early mechanisms in the pathway to B-cell maturation to reduce wasteful V(H)-(D(H))-J(H) recombination. Finally, similar to early immunoglobulin-H rearrangement patterns in the mouse, B cells of ALL derive from a pool of cells more immature than the cells in chronic lymphoid B-cell malignancies.

Adolescent↗
PubMed2000

Growth hormone and markers of immune function in children with renal transplants.

Lymphocyte subsets and T cell activation markers were measured in ten children with renal transplants for up to 1 year before and during their 1st year of recombinant human growth hormone (rhGH) treatment. The number of lymphocytes, helper or cytotoxic T cells or natural killer cells, and the T cell expression of CD25, CD26 and HLA-DR antigens were not altered by rhGH. B cell numbers declined both before and during treatment. There was no difference in lymphocyte subset numbers between children with and without rejection episodes.

Adolescent↗
PubMed1999

Posttransplantation lymphoproliferative disorder in liver recipients: characteristics, management, and outcome.

Posttransplantation lymphoproliferative disorder (PTLD) is a well-recognized complication of organ transplantation. The aim of this study, performed over 9 years, was to examine the histopathological findings, clinical course, and outcome of patients who, having undergone orthotopic liver transplantation (OLT), developed PTLD. The sample included 7 adult liver allograft recipients (1.7%), 4 men and 3 women, with a mean age of 53 years (range, 40 to 61 years) who developed PTLD 1 to 36 months post-OLT (mean, 6 months). Four patients received either antithymocyte globulin as primary immunosuppression or OKT3 for steroid-resistant cellular rejection. Four patients had localized hepatic tumor with or without regional lymph node involvement, 2 patients had extralymphoreticular disease (head of pancreas and chest wall), and 1 patient had spleen and lymph node involvement. All tumors were B-cell lymphomas; three polymorphic and four monomorphic. Clonality was assessed by immunostaining for kappa and lambda and gene rearrangement. Monoclonality was found in 4 patients and polyclonality in 2 (1 of whom progressed to monoclonality); in 2 patients, clonality could not be determined. Immunohistochemistry findings for the presence of the Epstein-Barr virus (EBV)-determined nuclear antigen and the latent membrane protein 1 were noted in lymphoma tissue in 6 patients. Immunosuppressive therapy was decreased in all patients. Polyclonal tumors were treated with acyclovir (1 patient is in complete remission and 1 patient died), and monoclonal tumors with systemic chemotherapy (2 patients are in complete remission and 2 patients died). One patient was treated with monoclonal antibodies (CD20) but failed to respond, and 1 patient was treated with excision and is in complete remission. The mortality rate was 43%; for the remainder, median survival is 21 months (range, 10 to 42 months). We conclude that PTLD may re-present early after OLT. EBV has a special role in the pathogenesis, combined with immunosuppressive therapy. The outcome is poor, and new therapeutic approaches are needed.

Adult↗
PubMed1997

Randomised trial of basiliximab versus placebo for control of acute cellular rejection in renal allograft recipients. CHIB 201 International Study Group.

BACKGROUND: Currently available immunosuppressive regimens for cadaver-kidney recipients are far from ideal because acute-rejection episodes occur in about 30% to 50% of these patients. In the phase III study described here we assessed the ability of basiliximab, a chimeric interleukin (IL)-2 receptor monoclonal antibody, to prevent acute-rejection episodes in renal allograft recipients. METHODS: 380 adult recipients of a primary cadaveric kidney transplant were randomly allocated, in this double-blind trial, to receive a 20 mg infusion of basiliximab on day 0 (day of surgery) and on day 4, to provide IL-2-receptor suppression for 4-6 weeks (n=193), or to receive placebo (n=187). Both groups received baseline dual immunosuppressive therapy with cyclosporin and steroids throughout the study. The primary outcome measure was incidence of acute-rejection episodes during the 6 months after transplantation. Safety and tolerability were monitored over the 12 months of the study. FINDINGS: 376 patients were eligible for intention-to-treat analysis (basiliximab, n=190; placebo, n=186). No significant differences in patient characteristics were apparent. The incidence of biopsy-confirmed acute rejection 6 months after transplantation was 51 (29.8%) of 171 in the basiliximab group compared with 73 (44.0%) of 166 in the placebo group (32% reduction; 14.2% difference [95% Kaplan-Meier CIs 3% to 24%], p=0.012). The incidence of steroid-resistant first rejection episodes that required antibody therapy was significantly lower in the basiliximab group (10% vs 23.1%, 13.1% difference [5.4% to 20.8%], p<0.001). At weeks 2 and 4 post-transplantation, the mean daily dose of steroids was significantly higher in the placebo group (p<0.001 with one-way analysis of variance). The incidence of graft loss at 12 months post-transplantation was 23 (12.1%) of 190 in the basiliximab group and 25 (13.4%) of 186 in the placebo group (1.3% difference [-5% to 9%], p=0.591). The incidence of infection and other adverse events was similar in the two treatment groups. The acute tolerability of basiliximab was excellent, with no evidence of cytokine-release syndrome. 14 deaths (basiliximab n=9; placebo n=5; -2.0% difference [-6% to 2%], p=0.293) occurred during the 12-month study and a further three deaths (basiliximab n=1; placebo n=2) occurred within the 380-day cut-off period. One post-transplantation lymphoproliferative disorder was recorded in each group. INTERPRETATION: Prophylaxis with 40 mg basiliximab reduces the incidence of acute rejection episodes significantly, with no clinically relevant safety or tolerability concerns.

Acute Disease↗
PubMed1997

Recombinant RFB4 immunotoxins exhibit potent cytotoxic activity for CD22-bearing cells and tumors.

Many B-cell malignancies express the CD22 antigen on their cell surface. To kill cells expressing this antigen, the RFB4 monoclonal antibody (MoAb) has been linked chemically with either deglycosylated ricin A chain or truncated versions of Pseudomonas exotoxin. These immunotoxins exhibited selective cytotoxic activity for CD22+ cells and antitumor activity in nude mouse models bearing human B-cell lymphomas. To construct a recombinant immunotoxin targeted to CD22, we first cloned the variable portions of the heavy and light chains of RFB4. The cloned Fv fragments were joined by a newly created disulfide bond to form a disulfide stabilized (ds) construct. The RFB4 construct was combined by gene fusion with PE38, a truncated version of PE. The recombinant immunotoxin was then expressed in Escherichia coli, purified by column chromatography and tested for cytotoxicity activity. RFB4(dsFv)PE38 retained its binding activity for CD22, was very stable at 37 degrees C and exhibited selective cytotoxic activity for CD22+-cultured cell lines. Because of its favorable binding characteristics and potency for CD22-positive cell lines, RFB4(dsFv)PE38 was tested for antitumor activity in a nude mouse model of human lymphoma. CA46 cells were injected subcutaneously and then treated with the RFB4(dsFv)PE38 immunotoxin. Antitumor activity was dose responsive and was not evident when an irrelevant immunotoxin was administered on the same schedule.

Amino Acid Sequence↗
PubMed1996

Clinical and pathological heterogeneity in cutaneous gamma-delta T-cell lymphoma: a report of three cases and a review of the literature.

Cutaneous gamma-delta (gamma delta) T-cell lymphoma is rare. Eleven cases have been reported to date including four cases of mycosis fungoides (MF), two of pagetoid reticulosis and five of pleomorphic cutaneous T-cell lymphoma (CTCL). We report three further cases of cutaneous gamma delta T-cell lymphoma; one of MF, one of a pleomorphic CTCL and one of a subcutaneous T-cell lymphoma. Combined data suggest that although cutaneous gamma delta T-cell lymphomas do not appear to comprise a single clinicopathological entity, they may be associated with aggressive clinical behaviour and a poor prognosis.

Adult↗
PubMed1995

Grading of cellular rejection after orthotopic liver transplantation.

All 684 post-orthotopic liver transplantation (OLT) liver biopsies performed at the Royal Free Hospital (RFH) between 1988 and 1993, from 120 patients, were reviewed in order to try to define the relative importance of the histological features of immunosuppression-responsive cellular rejection. Twenty histological features considered to be possible contributors to the diagnosis of cellular rejection were documented in a binary (present/absent) fashion. These features in 106 biopsy specimens obtained 1 to 8 days after OLT were analyzed using stepwise logistic discriminant analysis. All clinical and treatment records were reviewed, and each biopsy specimen was assigned to a diagnostic category depending on these records and follow-up information. Important determinants of the histological diagnosis of cellular rejection (which occurred in 84 of the 106 cases) were moderate/severe mixed portal inflammation, eosinophils, endotheliitis, and bile duct damage. When these all occurred together, the odds of rejection increased 3.6-fold. The original histological diagnosis was recorded, and each biopsy specimen showing cellular rejection was regarded according to the specific criteria of Snover et al., Demetris et al., and a novel RFH scoring system. The latter consists of evaluating portal inflammation, endotheliitis, eosinophils, and bile duct damage, each on a 0 to 3 scale (none, mild, moderate, or severe, respectively) and summation. The resulting cellular rejection score thus can range from 0 to 12. The agreement between the different scoring systems was analyzed using K statistics, and there was good concordance (K, 0.64 to 0.78), despite different histological criteria being used to derive each score. Each system showed a similar degree of sensitivity (87% to 96%). The specificity ranged from 59% to 77%. We conclude that the histological diagnosis of cellular rejection relies mainly on the previously described features of mixed portal inflammation, endotheliitis, eosinophils, and duct damage. There is scope for unification and simplification of the existing grading systems, which depend on differing criteria, and we suggest one such scheme.

Biopsy↗
PubMed1995

Up-regulation of endoglin on vascular endothelial cells in human solid tumors: implications for diagnosis and therapy.

We have characterized a murine IgM monoclonal antibody, TEC-11, that recognizes endoglin and may be suitable for targeting cytotoxic agents to human tumor vasculature. TEC-11 strongly stains endothelial cells in a broad range of solid human tumors while staining endothelial cells in the majority of normal, healthy adult tissues relatively weakly. Human umbilical vein endothelial cells (HUVECs) in sections of the umbilical vein react weakly with TEC-11, whereas proliferating HUVECs in tissue culture react strongly and uniformly. HUVEC cultures grown to confluence and then rested contain two subpopulations having high and low levels of endoglin expression. Flow cytometry revealed that a significant proportion of cells with high endoglin expression are cycling, having markedly increased levels of cellular protein, RNA, and DNA by comparison to low endoglin-expressing cells, which appear to be noncycling. Taken together, the increased binding of TEC-11 to tumor vasculature and to dividing as opposed to noncycling HUVECs in vitro suggests that endoglin is an endothelial cell proliferation-associated marker. An immunotoxin [TEC-11.deglycosylated ricin A chain (dgA)] composed of TEC-11 and dgA was 3000-fold more potent at inhibiting protein synthesis in proliferating HUVEC cultures than in confluent cultures. The confluent cells were no more sensitive to TEC-11.dgA than they were to an isotype-matched immunotoxin of irrelevant specificity. These findings suggest that TEC-11.dgA might have therapeutic value in the treatment of solid tumors in humans by selectively killing dividing endothelial cells which are prevalent in such tumors.

Adult↗
PubMed1994

Experimental treatment of human Hodgkin's disease with ricin A-chain immunotoxins.

In the present paper we describe the evaluation of ricin A-chain immunotoxins for clinical application in Hodgkin's disease. The immunotoxins were constructed by chemically linking deglycosylated ricin-A to monoclonal antibodies (MoAb) recognising lymphocyte activation markers CD25, CD30, or IRac, which are expressed by Hodgkin's and Reed-Sternberg (H-RS) cells. The cytotoxic effects of the immunotoxins were investigated in vitro against L540Cy Hodgkin cells and in vivo against Hodgkin's tumors in nude mice and disseminated Hodgkin's tumors in SCID mice. MoAbs were evaluated for crossreactivity with normal human tissues and staining of sections from Hodgkin's disease tissue. Of 32 MoAbs, eight showed little crossreactivity with vital human organs and produced highly active immunotoxins. The most effective immunotoxin, RFT5 gamma l.dgA (CD25), inhibits the growth of H-RS cells at concentrations of 7 x 10(-12) M. RFT5 gamma l.dgA destroys about 60% of solid Hodgkin's tumors of 0.5 cm diameter in nude mice and induces complete remissions in 95% of SCID mice with disseminated Hodgkin's tumors when administered one day after tumor challenge. This immunotoxin binds to all H-RS cells in more than 90% of patients with Hodgkin's disease. Patients with refractory Hodgkin's disease are currently being treated in a phase-I/II clinical trial.

Animals↗
PubMed1994

Variable kappa gene rearrangement in lymphoproliferative disorders: an analysis of V kappa gene usage, VJ joining and somatic mutation.

We have studied a diverse group of lymphoproliferative disorders (acute lymphoblastic leukaemia (ALL), chronic lymphocytic leukaemia (CLL), non-Hodgkin lymphoma (NHL) and myeloma) to determine if V kappa gene use is random or disease-specific and whether somatic mutations (a late event in B-cell differentiation) can provide additional information on the type of B cell involved in the neoplastic clone. In this group of disorders V kappa gene selection is not random and some members of each V kappa family are preferentially rearranged. V kappa genes from the distal portion of the locus are seldom used, possibly because rearrangement of the proximal locus by deletion is more efficient than rearrangement of the distal locus by inversion. Although pseudogenes account for 46% of the V genes in the kappa locus none were ever rearranged, even in non-functional rearrangements of lambda-producing leukemias, suggesting the existence of a mechanism which down-regulates the rearrangement of pseudogenes. N regions were noted at the VJ junction in 20% of alleles (in six CLL, three NHL, two ALL and one myeloma) possibly the result of kappa-chain recombination during the early period of B-cell maturation in which TdT is expressed. Nucleotide addition or imprecise joining at the VJ junction, resulting in a shift in the reading frame, were the commonest causes of non-functional rearrangement. The occurrence of somatic mutation broadly correlated with the stage of B-cell maturation from which the different disorders are thought to arise. However, there was no strict association and somatic mutations were demonstrated in 'typical CLL' while V kappa genes were germline in some follicular lymphomas; these findings suggest either heterogeneity in the stage of B-cell maturation at which these disorders arise or some variability in the process of somatic mutation.

Alleles↗
PubMed1993

Delivery of saporin to human B-cell lymphoma using bispecific antibody: targeting via CD22 but not CD19, CD37, or immunoglobulin results in efficient killing.

A panel of bispecific F(ab')2 antibodies (BsAb) have been constructed for delivering the ribosome-inactivating protein saporin to human B cell lymphoma. Each derivative was prepared with specificity for saporin and CD19, CD22, CD37, or immunoglobulin. In vitro studies measuring inhibition of [3H]leucine uptake by cultured Daudi and Raji cells demonstrated that, despite all BsAb capturing saporin on the cell surface, BsAb targeting through CD22 were far more cytotoxic than those functioning via CD19, CD37, or surface immunoglobulin. This exceptional activity of the CD22-specific BsAb appears to derive from its ability to deliver and accumulate saporin inside the target cells. Further studies showed that four CD22-specific BsAb all performed with equal potency and were able to increase saporin toxicity (50% inhibitory concentration) up to 1000-fold, from 2 x 10(-7) M to 2 x 10(-10) M. Pairs of anti-CD22 BsAb which recognized different nonblocking epitopes on the saporin molecule were able to bind saporin more avidly to the target cell and, as a consequence, increased cytotoxicity by at least an additional 10-fold, resulting in 50% inhibitory concentration for protein synthesis of 2 x 10(-11) M. These results suggest that selected combinations of BsAb which bind cooperatively to a toxin and the cell surface may provide an efficient way of delivering toxins to unwanted cells in patients.

Antibodies, Monoclonal↗
PubMed1993

Protection of germinal centres from complement attack: decay-accelerating factor (DAF) is a constitutive protein on follicular dendritic cells. A study in reactive and neoplastic follicles.

The development of B-cell memory is linked to the presence of germinal centres. This process is dependent on the presence of antigen, usually in the form of immune complexes with antibody, on the surface of the follicular dendritic cells (FDCs) that form a network in the germinal centre. The presence of immune complexes poses a constant danger of activating complement. Decay accelerating factor (DAF, CD55) and the membrane attack complex (MAC) inhibitor (CD59) are two cell proteins whose sole function is to protect cells from the action of complement, the former affecting the earlier components of the complement cascade, and the latter the terminal ones; both are bound to the cell surface via a glycosylphosphatidylinositol link. DAF but not CD59 could be demonstrated on FDCs. DAF is also present on the FDCs in follicular lymphomas despite the absence of complement (C3) in neoplastic follicles. This indicates that DAF is constitutive to FDCs but does not preclude the possibility that its expression is increased when immune complexes are deposited.

Antigens, CD↗